Re: [BULK] Re: CMIPCI driver. IEC958 user data and channel status

Re: [BULK] Re: CMIPCI driver. IEC958 user data and channel status

[Assaf Hoffman]

Hi,
Thank you for your answer.
I would be happy if you could address the following correlated
questions:
1) According to your experience, is it correct to assume that once a PCM

   instance for playback/capture is prepared and triggered, the user
data 
   and channel status are constants during data transmit/receive?
2) In the case HW saves the user data and channel status in its internal

   registers, how would the ALSA stack know if any of them changed?
3) Is there a bridge application in the ALSA stack? I mean, in case 
   I would like to capture ICE958 frames and route them to ICE958
playback 
   channel.

Thanks.

-----Original Message-----
From: Takashi Iwai [mailto:tiwai@suse.de] 
Sent: Tuesday, October 17, 2006 12:58 PM
To: Assaf Hoffman
Cc: alsa-devel@lists.sourceforge.net; Rita Shtern
Subject: [BULK] Re: [Alsa-devel] CMIPCI driver. IEC958 user data and
channel status
Importance: Low

At Mon, 16 Oct 2006 13:41:02 +0200,
Assaf Hoffman wrote:
> 
> Hi,
> As I understand, the IEC958 frame incorporates not only sound sample
but
> also other information such as user data and channel status.
> I could not locate in the CMIPCI driver where the user data or channel
> status is read/write from/to the device and where is it kept on DRAM.

This depends on the chip model.  With the earlier chip, you have to
use 32bit SPDIF "raw" data including SPDIF status bits and data.
The soft_ac3 corresponding to this.  In the ALSA framework, alsa-lib
encodes/decodes the SPDIF raw data.

The recent version of chip has some register bits to indicate the
non-audio data.  The driver sets them up accordingly.
Then the 16bit data is handled as is without modification.


Takashi

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Re: [BULK] Re: CMIPCI driver. IEC958 user data and channel status

[Takashi Iwai]

At Tue, 17 Oct 2006 13:16:57 +0200,
Assaf Hoffman wrote:
> 
> Hi,
> Thank you for your answer.
> I would be happy if you could address the following correlated
> questions:
> 1) According to your experience, is it correct to assume that once a PCM
> 
>    instance for playback/capture is prepared and triggered, the user
> data 
>    and channel status are constants during data transmit/receive?
> 2) In the case HW saves the user data and channel status in its internal
> 
>    registers, how would the ALSA stack know if any of them changed?
> 3) Is there a bridge application in the ALSA stack? I mean, in case 
>    I would like to capture ICE958 frames and route them to ICE958
> playback 
>    channel.

If you think of cmipci, the hardware doesn't create any IEC958 status
bits for _input_.  What I explained about the SPDIF output.


Takashi

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Re: [BULK] Re: CMIPCI driver. IEC958 user data and channel status

[Assaf Hoffman]

Hi	
Thank you for your answer.
Could you please address the question below with no relevance to CMIPCI
driver?
Many thanks.

-----Original Message-----
From: Takashi Iwai [mailto:tiwai@suse.de] 
Sent: Wednesday, October 18, 2006 1:28 PM
To: Assaf Hoffman
Cc: Rita Shtern; alsa-devel@lists.sourceforge.net
Subject: Re: [Alsa-devel] [BULK] Re: CMIPCI driver. IEC958 user data and
channel status
Importance: Low

At Tue, 17 Oct 2006 13:16:57 +0200,
Assaf Hoffman wrote:
> 
> Hi,
> Thank you for your answer.
> I would be happy if you could address the following correlated
> questions:
> 1) According to your experience, is it correct to assume that once a
PCM
> 
>    instance for playback/capture is prepared and triggered, the user
> data 
>    and channel status are constants during data transmit/receive?
> 2) In the case HW saves the user data and channel status in its
internal
> 
>    registers, how would the ALSA stack know if any of them changed?
> 3) Is there a bridge application in the ALSA stack? I mean, in case 
>    I would like to capture ICE958 frames and route them to ICE958
> playback 
>    channel.

If you think of cmipci, the hardware doesn't create any IEC958 status
bits for _input_.  What I explained about the SPDIF output.


Takashi

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Re: [BULK] Re: CMIPCI driver. IEC958 user data and channel status

[Takashi Iwai]

At Wed, 18 Oct 2006 13:31:39 +0200,
Assaf Hoffman wrote:
> 
> Hi	
> Thank you for your answer.
> Could you please address the question below with no relevance to CMIPCI
> driver?

Then it depends on the driver implementation.
Usually the driver provides "IEC958 Capture xxx" control elements
(either IFACE_PCM or IFACE_MIXER attribute) so that the apps can
extract the SPDIF status bits via control API.


Takashi

> Many thanks.
> 
> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai@suse.de] 
> Sent: Wednesday, October 18, 2006 1:28 PM
> To: Assaf Hoffman
> Cc: Rita Shtern; alsa-devel@lists.sourceforge.net
> Subject: Re: [Alsa-devel] [BULK] Re: CMIPCI driver. IEC958 user data and
> channel status
> Importance: Low
> 
> At Tue, 17 Oct 2006 13:16:57 +0200,
> Assaf Hoffman wrote:
> > 
> > Hi,
> > Thank you for your answer.
> > I would be happy if you could address the following correlated
> > questions:
> > 1) According to your experience, is it correct to assume that once a
> PCM
> > 
> >    instance for playback/capture is prepared and triggered, the user
> > data 
> >    and channel status are constants during data transmit/receive?
> > 2) In the case HW saves the user data and channel status in its
> internal
> > 
> >    registers, how would the ALSA stack know if any of them changed?
> > 3) Is there a bridge application in the ALSA stack? I mean, in case 
> >    I would like to capture ICE958 frames and route them to ICE958
> > playback 
> >    channel.
> 
> If you think of cmipci, the hardware doesn't create any IEC958 status
> bits for _input_.  What I explained about the SPDIF output.
> 
> 
> Takashi
> 

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Re: [BULK] Re: CMIPCI driver. IEC958 user data and channel status

[Clemens Ladisch]

Assaf Hoffman wrote:
> 1) According to your experience, is it correct to assume that once a PCM
>    instance for playback/capture is prepared and triggered, the user data 
>    and channel status are constants during data transmit/receive?

Many drivers assume this for playback, i.e., they set these bits once when
the PCM stream is configured.

When capturing, these bits could change at any time, depending on the
source.  Most drivers allow to read the current values of these bits.

> 2) In the case HW saves the user data and channel status in its internal
>    registers, how would the ALSA stack know if any of them changed?

It wouldn't know at all, unless the hardware can issue an interrupt for
this situation.

There is a flag SNDRV_CTL_ELEM_ACCESS_VOLATILE for controls that can
change their value without notification.

> 3) Is there a bridge application in the ALSA stack? I mean, in case 
>    I would like to capture ICE958 frames and route them to ICE958 playback 
>    channel.

It would be possible to write an application that records and then plays
back the data, or to pipe the output of arecord into aplay.  ALSA
doesn't have any built-in functionality for that.


HTH
Clemens

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